# Bourbaki theory of isomorphism, examples of untransportable formulas

In their book "Theory of sets" Bourbaki suggested a general theory of isomorphism.

The example of an untransportable relation (i.e. formula) in the book involves 2 principal base sets.

Are there examples of untrasportable formulas when we allow only one principal base set?

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Very few people here are familiar with Bourbaki's set theory. You should probably state the definitions here as well. – Harry Gindi Jun 19 '10 at 12:14
A reference is added in the question. – Victor Makarov Jun 22 '10 at 13:44